In the manufacturing industry, and in particular manufacturing industries that rely on assembly lines, such as the automotive industry, it has become commonplace for automobile manufactures to assemble cars using modular assemblies/subassemblies (including, without limitation, housings, brackets, plates, panels, heads, blocks, rails, harnesses, frames, etc.) that are shipped to the automobile manufactures from outside vendors. Using modular assemblies/subassemblies allows the automobile manufacturer to increase productivity by reducing the amount of assembly that needs to occur at the manufacturing plant. In order to further facilitate the manufacturing process, it is common for modular assemblies/subassemblies to include the bolts or other fasteners that the manufacturer will use to attach the modular assembly/subassembly to another component in the automobile. These bolts are placed in their respective clearance holes in the modular assembly/subassembly before shipping to the manufacturer and thus eliminate the need for a line technician at the assembly plant to retrieve the appropriate-sized bolt and use it to connect the subassembly to the main assembly. Thus, using a modular assembly/subassembly with connecting bolts already in place allows the assembly plant to merely align the assembly/subassembly with its mating structure, advance the bolts by hand until the threads on the bolt and the threads in the mating structure engage and then use whatever tool is typically used to tighten the bolts (i.e., ratchets, pneumatic wrenches, screwdrivers, etc.).
A problem that has plagued manufactures of these modular assemblies/subassemblies that are shipped to automobile manufactures is that the bolts used to connect the modular assemblies to other mating components of the automobile very often fall out of their respective clearance holes due to the shipping process. Although bolt retention systems have been used by these manufacturers, such as polymer compositions extruded onto threads of a bolt, failures nonetheless occur, which is unacceptable to the automobile manufactures and can be costly to the particular vendor. Indeed, if an automobile manufacturer receives modular assemblies/subassemblies with missing or misplaced connecting bolts, such an occurrence could lead to the automobile manufacturer canceling a particular vendor's contract or, if such missing or misplaced bolts cause an assembly line to shut down, the automobile manufacturer can charge the vendor for the amount of money lost for the down time, which can be on the order of magnitude of $1000 per minute.
Besides the shipping process, which can cause severe oscillations that tend to cause shippable in-assembly bolts to fall out of their clearance holes, the bolt retention system must be chemically inert so that it maintains its retention properties in environments such as petroleum-based lubricants, which are common in the automotive field. A retention material that deteriorates in chemical environments typically found in these assemblies/subassemblies will invariable lose their retention properties, leading to failures of the retention system. Also, a retention material that is not chemically inert can cause the opposite effect and freeze the bolt (because the retention system bonds to the clearance holes in the assembly/subassembly) or increase the coefficient of friction, thus making it very difficult for a manufacturer to use the bolt and assembly/subassembly.
Because an assembly bolt will typically have to be advanced at least ¼ of an inch before the threads can engage, it is important that whatever retention system is used with in-assembly bolts not have axial forces that prevent an assembler from pushing the bolt within its clearance hole by hand to engage the threads. Also, due to efficiency concerns, a retention system must not need to be removed by an assembly worker prior to installation. In other words, the retention system must be able to remain in the assembly/subassembly for the life of the part without interfering with the operation of the assembly/subassembly or the automobile as a whole.
Accordingly, automobile manufacturers have demanded that manufactures of assemblies/subassemblies develop so-called shippable in-assembly bolts have certain minimum characteristics, namely that the bolts (i) remain in their respective assembly/subassembly clearance holes during shipment and subsequent handling; (ii) retain ease of installation with their mating assemblies or subassemblies; (iii) not contain any components that need to be removed prior to assembly with their respective assemblies or subassemblies; (iv) the bolt retention materials must be chemically inert with chemicals, adhesives, grease or other petroleum-based lubricants, or any other chemical used in the mating assembly/subassembly; (v) be compatible with hand assembly operations as well as semi-automated and automated assembly operations; and (iv) substantially maintain its axial retention and torsional force values for at least 30 days. Lastly, the retention system on the shippable in-assembly bolts must not be too expensive, otherwise the cost of the assembly/subassembly will not be palatable to the automobile manufacturer and/or the vendor will have to reduce its profit margins.
Accordingly, there is a need for a shippable in-assembly bolt that addresses the above identified problems. Other needs will become apparent based on a review of the specification, claims and drawings herein.